22-06-2012, 04:05 PM
WIRELESS COMMUNICATIONS
[attachment=25112]
INTRODUCTION:
The first operational cellular communication system was deployed in the Norway in 1981 and was followed by similar systems in the US and UK. These first generation systems provided voice transmissions by using frequencies around 900 MHz and analogue modulation.
The second generation (2G) of the wireless mobile network was based on low-band digital data signaling. The most popular 2G wireless technology is known as Global Systems for Mobile Communications (GSM). The first GSM systems used a 25MHz frequency spectrum in the 900MHz band.
Planning for 3G started in the 1980s. Initial plans focused on multimedia applications such as videoconferencing for mobile phones. When it became clear that the real killer application was the Internet, 3G thinking had to evolve. As personal wireless handsets become more common than fixed telephones, it is
clear that personal wireless Internet access will follow and users will want broadband Internet access wherever they go.
Migrating to 4G:
The fact that 4G mobile networks intend to integrate almost every wireless standard already In use, enabling its simultaneous use and interconnection poses many questions not yet answered. The research areas that present key challenges to migrate current systems to 4G are many but can be summarized in the following: Mobile Station, System and Service. [7] To be able to use 4G mobile networks a new type of mobile terminals must be conceived. The terminals to be adopted must adapt seamless to multiple wireless networks, each with different protocols and technologies. Auto reconfiguration will also be needed so that terminals can adapt to the different services available.
GENERIC MIMO AND OFDM:
Increasing demand for high performance 4G broadband wireless mobile calls for
use of multiple antennas at both base station and subscriber ends. Multiple
antenna technologies enable high capacities suited for Internet and multimedia services and also dramatically increase range and reliability. This design is motivated by the growing demand for broadband wireless Internet access. The challenge for wireless broadband access lies in providing a comparable quality of service for similar cost as competing wire line technologies. The target frequency band for this system is 2 to 5 GHz due to favorable propagation characteristics and low radio-frequency (RF) equipment cost. The broadband channel is typically non LOS channel and includes impairments such as time selective fading and frequency-selective fading. Multiple antennas at the transmitter and receiver provide diversity in a fading environment. By employing multiple antennas, multiple spatial channels are created and it is unlikely all the channels will fade simultaneously.
OPENWIRELESSARCHITECTURE
The 4G Mobile communications will be based on the Open Wireless Architecture (OWA)to ensure the single terminal can seamlessly and automatically connect to the local high-speed wireless access systems when the users are in the offices, homes, airports or shopping centers where the wireless access networks (i.e. Wireless LAN, Broadband Wireless Access, Wireless Local Loop, HomeRF, Wireless ATM, etc) are available. When the users move to the mobile zone (i.e. Highway, Beach, Remote area, etc.),the same terminal can automatically switch to the wireless mobile networks (i.e.GPRS,W-CDMA,cdma2000, TD-SCDMA, etc.).This converged wireless communications can provide the following advantages.
GOAL:
The goal of 4th Generation (4G) mobile communications technologies is to realize wireless communications at the same high data rate as is made possible through use of the fiber-optic transmission systems that are available today. Realization of 4G mobile communications is foreseen in the early 2010s, but various precursor technologies and services have been appearing as of late. A scrutiny on the market trends, along with a close watch on carrier reaction as to the introduction of the Mobile Number Portability (MNP) system planned for October 24, 2006, is of vital importance at this time for all those interested in this business field.
Conclusion:
In this paper we present the evolution of mobile communications through all its generations. From the initial speech vocation to an IP-based data network, several steps were made. From the analog voice centric first generation to the digital second generation, the goal was to enhance the voice experience of a user, by improving the quality of the communication while using more efficiently the installed capacity. At the same time the enhanced mobility provided by seamless handover and the additional data communications capacity (although very small) advanced and opened the doors to future developments Some of the developments was brought by generation 2.5 namely by GPRS, which improved data communications by supporting IP in the GSM infrastructure. With the third generation the goal changed from voice-centric to data-centric. Moreover total obility became an objective to pursuit.
[attachment=25112]
INTRODUCTION:
The first operational cellular communication system was deployed in the Norway in 1981 and was followed by similar systems in the US and UK. These first generation systems provided voice transmissions by using frequencies around 900 MHz and analogue modulation.
The second generation (2G) of the wireless mobile network was based on low-band digital data signaling. The most popular 2G wireless technology is known as Global Systems for Mobile Communications (GSM). The first GSM systems used a 25MHz frequency spectrum in the 900MHz band.
Planning for 3G started in the 1980s. Initial plans focused on multimedia applications such as videoconferencing for mobile phones. When it became clear that the real killer application was the Internet, 3G thinking had to evolve. As personal wireless handsets become more common than fixed telephones, it is
clear that personal wireless Internet access will follow and users will want broadband Internet access wherever they go.
Migrating to 4G:
The fact that 4G mobile networks intend to integrate almost every wireless standard already In use, enabling its simultaneous use and interconnection poses many questions not yet answered. The research areas that present key challenges to migrate current systems to 4G are many but can be summarized in the following: Mobile Station, System and Service. [7] To be able to use 4G mobile networks a new type of mobile terminals must be conceived. The terminals to be adopted must adapt seamless to multiple wireless networks, each with different protocols and technologies. Auto reconfiguration will also be needed so that terminals can adapt to the different services available.
GENERIC MIMO AND OFDM:
Increasing demand for high performance 4G broadband wireless mobile calls for
use of multiple antennas at both base station and subscriber ends. Multiple
antenna technologies enable high capacities suited for Internet and multimedia services and also dramatically increase range and reliability. This design is motivated by the growing demand for broadband wireless Internet access. The challenge for wireless broadband access lies in providing a comparable quality of service for similar cost as competing wire line technologies. The target frequency band for this system is 2 to 5 GHz due to favorable propagation characteristics and low radio-frequency (RF) equipment cost. The broadband channel is typically non LOS channel and includes impairments such as time selective fading and frequency-selective fading. Multiple antennas at the transmitter and receiver provide diversity in a fading environment. By employing multiple antennas, multiple spatial channels are created and it is unlikely all the channels will fade simultaneously.
OPENWIRELESSARCHITECTURE
The 4G Mobile communications will be based on the Open Wireless Architecture (OWA)to ensure the single terminal can seamlessly and automatically connect to the local high-speed wireless access systems when the users are in the offices, homes, airports or shopping centers where the wireless access networks (i.e. Wireless LAN, Broadband Wireless Access, Wireless Local Loop, HomeRF, Wireless ATM, etc) are available. When the users move to the mobile zone (i.e. Highway, Beach, Remote area, etc.),the same terminal can automatically switch to the wireless mobile networks (i.e.GPRS,W-CDMA,cdma2000, TD-SCDMA, etc.).This converged wireless communications can provide the following advantages.
GOAL:
The goal of 4th Generation (4G) mobile communications technologies is to realize wireless communications at the same high data rate as is made possible through use of the fiber-optic transmission systems that are available today. Realization of 4G mobile communications is foreseen in the early 2010s, but various precursor technologies and services have been appearing as of late. A scrutiny on the market trends, along with a close watch on carrier reaction as to the introduction of the Mobile Number Portability (MNP) system planned for October 24, 2006, is of vital importance at this time for all those interested in this business field.
Conclusion:
In this paper we present the evolution of mobile communications through all its generations. From the initial speech vocation to an IP-based data network, several steps were made. From the analog voice centric first generation to the digital second generation, the goal was to enhance the voice experience of a user, by improving the quality of the communication while using more efficiently the installed capacity. At the same time the enhanced mobility provided by seamless handover and the additional data communications capacity (although very small) advanced and opened the doors to future developments Some of the developments was brought by generation 2.5 namely by GPRS, which improved data communications by supporting IP in the GSM infrastructure. With the third generation the goal changed from voice-centric to data-centric. Moreover total obility became an objective to pursuit.